It is of significant interest to determine the properties of multi-phase systems such as dispersions, emulsions and the like.
One example of a multi-phase system is that formed by hydrocolloids such as starch granules and rice grains swollen by water, particularly during a cooking process. The swell volumes of such systems are of particular interest as an aid to determining the potential suitability of particular starches in different applications, especially in the food industry. Currently, the swell volume is determined by cooking a predetermined quantity of starch granules in a known volume of water, placing the resultant multi-phase system in a laboratory measuring cylinder and allowing it to settle for 24 hours, following which the volume of the settled starch may be read from the cylinder. Clearly, the acquisition of data by this method is laborious and costly.
Another type of multi-phase system of interest, in the beverages industry, involves oil-in-water emulsions consisting inter alia of water, flavouring oils, stabilisers such as gum Arabic, colorants and other additives. As many beverages are required to have long shelf lives, it is important that any emulsion system used in such beverages is stable over a long period of time. Consequently, instabilities in the emulsion systems typically, unless unusually unstable, may take at least one month, if not longer, to become visually apparent to human observers of the systems. Such time frames to determine stability/instability of this type of emulsion system results in both the slow development of new emulsions and the slow identification of solutions to technical problems such as shear instability, raw material quality etc.
As will be well understood, there are many other applications in which the properties of multi-phase systems are of particular interest in which similar problems arise. It will be appreciated that, whilst in many applications the stability of such systems is of interest, in other applications the ability to destabilise such systems may be a primary aim.
It has been proposed in U.S. Pat. No. 5,783,826 to identify data from multi-phase systems using equipment consisting of a housing for a movable electromagnetic emitter and detector system and into which a cell containing a sample may be inserted and held vertically. The emitter/detector system is operable to measure backscattered radiation from the sample therein. If desired, radiation transmitted through the sample in the cell may also be acquired. By moving the emitter/detector system stepwise relative to the cell, a phase profile of the sample may be generated. Repetition of the cycle at time intervals may reveal changes in the phase profile indicative of instability in the sample. However, again this is time consuming and, if large numbers of multi-phase systems are to be examined, of high capital expenditure to provide sufficient numbers of equipment to deal with such numbers.
U.S. Pat. No. 6,466,319 discloses determining the stability of a liquid suspension by maintaining the particles therein uniformly suspended, for example by stirring, whilst immersing a measuring cell therein and determining the amount of backscatter generated by particles that have increased in size, for example by agglomerating or through some other aggregation mechanism.
U.S. Pat. No. 6,691,057 is similar to U.S. Pat. No. 5,783,826 except that it proposes irradiating the full length of the sample cell with the radiation to obtain a simultaneous scan of all points along the cell thereby avoiding errors generated by potentially rapid changes within the multi-phase system which may occur during a linear scan as proposed in U.S. Pat. No. 5,783,826. Additionally, U.S. Pat. No. 6,691,057 also discloses accelerating any settlement process in the cell by tilting the cell as an aid to gravitational settlement. The emitter/detector system is also tilted to maintain the orientation between it and the sample cell.